Organosilanes or organosiloxanes have been used for many years to impregnate porous, mineral building materials, in order to protect these against penetration by water. It is particularly important for this hydrophobizing treatment that the active ingredients penetrate deeply into the building material and combine chemically or physically with it.
Penetration into the building material is favored if compounds with the lowest possible molecular weight are used as active, organosilicon ingredients. The depth of penetration can be improved additionally by also using organic solvents, which evaporate after use. High reactivity is attained if, as organosilicon compounds, organoalkoxysilanes and/or organoalkoxysiloxanes are used, which can condense in the presence of moisture and react with the building material. During such a reaction, the alcohol, corresponding to the alkoxy group, is split off and evaporated into the atmosphere.
Such a preparation is known from the German patent 33 12 911. It contains organoalkoxysiloxanes of the general formula ##STR3## wherein R.sup.1 is an alkyl or aryl group,
R.sup.2 is an alkyl group with 1 to 4 carbon atoms, PA1 a=0.8 to 1.5 and PA1 b.ltoreq.2. PA1 (a) 1 to 20% by weight of a mixture of organoalkoxysiloxanes of the aforementioned formula, which consists of 25 to 75% by weight of a siloxane, in which b=0.1 to 0.5 and 75 to 25% by weight of a siloxane, in which b=0.8 to 2.0, a+b being.ltoreq.3, PA1 (b) 80 to 99% by weight of a water-immiscible solvent and PA1 (c) optionally, known condensation catalysts. PA1 R.sup.2 is methyl or ethyl, PA1 a=u to 1.5 PA1 b=1.0 to 4.0 PA1 a+b=2.0 to 4.0 PA1 (a) 1 to 40% by weight of a hydrolyzable silane with a molecular weight of up to about 500 and the general formula R.sub.n Si(R').sub.4-n, wherein R is an optionally halogenated hydrocarbon group with 1 to 20 carbon atoms, R' is an alkoxy group with 1 to 3 carbon atoms or a halogen, amino or carboxyl group, n=1 or 2, or oligomers of these silanes and PA1 (b) 0.5 to 50% by weight based on the silane, of an emulsifier with an HLB value of 4 to 15 and PA1 (c) water. PA1 R.sup.1 is an alkyl group with 3 to 12 carbon atoms and PA1 R.sup.2 a methyl or ethyl group; PA1 a=0.8 to 1.2 and PA1 b=0.2 to 1.2; PA1 0.01 to 5% by weight of an emulsifier; PA1 0.01 to 0.1% by weight of fillers with an effective surface area of at least 40 m.sup.2 /g; and PA1 49.9 to 95.48% by weight of water. PA1 (a) if the emulsifier content is low, and PA1 (b) the emulsion contains hydrophobic silica and PA1 (c) a curing catalyst for the organosilicon compounds. PA1 1 means that there is no wetting of the contact surface; PA1 2 means that 50% of the contact area has been wetted; PA1 3 means that 100% of the contact area has been wetted; PA1 4 means water has been partly absorbed; the contact area is slightly dark; PA1 5 means that at least 50% of the water has been absorbed; the contact area is darker; PA1 6 means that the drop has been absorbed completely; the contact area is quite dark; and PA1 7 means that the drop of water has been absorbed completely in less than 5 minutes. PA1 a) 5 to 45% by weight of an alkoxysilane of the general formula EQU R.sup.1 --Si--(OR.sup.2).sub.3 PA1 wherein PA1 b) 45 to 5% by weight of a mixture consisting of a PA1 c) 0.5 to 10% by weight of an O/W emulsifier or emulsifier mixture; and PA1 d) 40 to 49.5% by weight of water. PA1 (1) R.sup.3 is an aminoalkyl group, the alkyl group of which has 1 to 6 carbon atoms. Examples of such groups are the ethylamine, propylamine, butylamine and hexylamine groups, the --(CH.sub.2).sub.3 --NH.sub.2 and ##STR8## groups being preferred. (2) R.sup.3 is a group of the general formula H.sub.2 N--(CH.sub.2).sub.x R.sup.4 --(CH.sub.2).sub.y --, in which R.sup.4 represents an oxygen, sulfur, --NH-- or --NH--CH.sub.2 --CH.sub.2 --NH group and x.gtoreq.2 and y=2. Examples of such groups are H.sub.2 N--(CH.sub.2).sub.3 -- and H.sub.2 N--(CH.sub.2).sub.2 --NH--(CH.sub.2).sub.3 --. PA1 (3) (R.sup.2 O).sub.3 Si--(CH.sub.2).sub.x --NH--(CH.sub.2).sub.x --. Examples of such groups are (C.sub.2 H.sub.5 O).sub.3 Si--(CH.sub.2).sub.3 --NH--(CH.sub.2).sub.3 -- and (CH.sub.3).sub.3 Si--(CH.sub.2).sub.2 --NH--(CH.sub.2).sub.2 --. PA1 (4) R.sup.3 is a group of the general formula ##STR9## n is a whole umber from 1 to 5. An example of a particularly preferred epoxide is ##STR10## PA1 20 to 30% by weight of component a). PA1 30 to 20% by weight of component b1)+b2) in the ratio of 4:3 PA1 3 to 7% by weight of emulsifier PA1 47 to 43% by weight of water. PA1 R.sup.7 is an alkyl group with 1 to 4 carbon atoms PA1 a=0.8 to 1.2 and PA1 b=0.2 to 1.2.
This preparation is characterized in that it consists of
The essential characteristic of this preparation accordingly consists of carrying out the impregnation not with an organoalkoxysiloxane, the molecular weight distribution of which has only a single maximum, but with a mixture of organoalkoxysiloxanes, the distinguishing feature of which is the different degrees of condensation. By these means, a great depth of penetration, associated with a high effectiveness, particularly on alkaline building materials and a good, optically visible water beading effect are assured.
The preparations described in the German patent 33 12 911 have proven their value in practice. An improvement in these preparations is possible essentially only with respect to the depth of penetration achievable in practice. This depth of penetration is affected essentially by three factors, namely the solvent used, the porosity of the building materials and the care, with which this preparation is applied in practice. Improved impregnating preparations must therefore be rated particularly on the basis of their penetration behavior.
As a result of greater environmental consciousness, the use of organic solvents is increasingly considered to be unacceptable. Special efforts have therefore been made to develop comparable preparations on an aqueous basis.
Further development work has led to a method, which is the object of the German patent 36 27 060. This patent relates to a method for impregnating mineral building materials, particularly masonry, with aqueous solutions of silanols and/or siloxanols, which are synthesized at the site of their use by hydrolysis of alkoxysilanes and/or alkoxysiloxanes. As alkoxysilanes and/or alkoxysiloxanes, compounds of the general formula ##STR4## wherein R.sup.1 is an alkyl group with 1 to 8 carbon atoms, at least 90% of the R.sup.1 groups in the average molecule being alkyl groups with 1 to 4 carbon atoms,
are selected. These compounds are hydrolyzed continuously in an amount corresponding to their use. The solution obtained is then, after mixing the reactants, applied on the mineral building material within a period of 3 to 30 minutes.
With this procedure, a high penetration of the aqueous preparations into the mineral building materials is achieved. This penetration is comparable with that achieved when solvent-containing preparations are used.
Because of their instability, these aqueous solutions must, as is required in the German patent 36 27 060, be synthesized at the location where they are to be used.
For the purpose of hydrophobizing ceramic materials, published European patent application 02 34 024 discloses an aqueous silane emulsion, which consists essentially of
Octyltriethoxysilane is named as a particularly preferred silane. In actual fact, emulsions of such silanes, in which the R group has more than 6 carbon atoms, have a better stability, since the rate of hydrolysis of these reactive silanes is decreased It is, however, a disadvantage that the hydrolysis of these silanes in the building material also necessarily takes place correspondingly slowly and must be catalyzed in a suitable manner. In some building materials, such as fresh concrete, this is possible due to the high alkalinity of this material. In neutral or weakly alkaline building materials, such as calcined clinker and numerous natural stones, this is not possible. Without such a catalysis, however, there is no anchoring of the silanes at the surface of the building material. The silanes can evaporate from the surface or be removed mechanically. This leads to a depletion of silane at the surface and, with that, to a reduced hydrophobization. As a consequence, the water-beading effect is weak or not present at all. The water absorption capacity in the depleted surface layer is high, so that especially this layer, which is particularly exposed to weathering and mechanical attack, is insufficiently protected. These preparations accordingly can be used only with certain building materials.
An impregnating emulsion with a good effect on alkaline and neutral building materials is described in the German Offenlegungsschrift 39 11 479. It contains 2.5 to 25% by weight of an alkoxysilane of the general formula EQU R.sup.1 --Si(OR.sup.2).sub.3 I
wherein
2 to 20% by weight of an alkoxysiloxane of the general formula ##STR5## wherein R.sup.3 is an alkyl group with 1 to 6 carbon atoms,
This impregnating emulsion generally has good water-repellent and beading effects on alkaline as well as on neutral mineral substrates. If the effects achieved with this emulsion are graded according to the procedure given below, it turns out that the best results are achieved
At a low emulsifier content, however, the impregnating emulsin is stable for only a limited time. If hydrophobic silica is contained in the emulsion, it frequently settles out on storage, making careful stirring at the site of use, that is, at the building site, necessary. Sufficient care is not always taken. Finally, the curing catalyst limits the time available for processing the emulsion and can lead to premature curing of the active ingredient of the emulsion during storage.